1. Field of Invention
The present invention relates to a method of producing a standard seawater solution for nutrient salt measurement to be used as an indicator for measuring a nutrient salt concentration in seawater for a purpose of an oceanographic survey or the like.
2. Description of Related Art
As is well known, when an oceanographic survey or the like is conducted, there may be given measurement of a nutrient salt concentration in seawater as a basic item. In that case, in order to collect measurement data regarding a concentration of a nutrient salt in actual seawater as a sample, it is convenient to produce and use a standard seawater solution for nutrient salt measurement as an indicator. Note that the nutrient salt as used herein refers to salts required for producing microorganisms, for example, salts such as a nitrate, a nitrite, a phosphate, a silicate, and an ammonium salt.
As this type of standard seawater solution for nutrient salt measurement (hereinafter also referred to simply as “standard seawater solution”), there may be given one produced through use of seawater as a material as disclosed in JP 3477468 B2 described below. In addition, JP 3477468 B2 discloses a method of producing a standard seawater solution through use of seawater as a material comprising, as basic steps, a filtering treatment step of filtering a plurality of kinds of material seawater having different nutrient salt concentrations collected from places at different water depths in a predetermined sea area, a mixing treatment step of mixing the plurality of kinds of material seawater in a predetermined ratio, and a sterilization treatment step of killing microorganisms in the material seawater by heating or the like.
Further, JP 3477468 B2 discloses that the method of producing a standard seawater solution further comprises a bottling step comprising pouring the treated seawater after the above-mentioned sterilization treatment into a resin bottle and hermetically sealing the resin bottle in a clean environment and a sealing step comprising covering an outer surface of the hermetically sealed resin bottle with a film-like material and sealing the resin bottle therein by reduced pressure suction.
Further, JP 4459752 B2 described below discloses that, when seawater containing nutrient salts is subjected to sterilization treatment including at least heating treatment while being stored in a large-capacity container, the seawater containing nutrient salts is subjected to the sterilization treatment while being stored in a large-capacity container made of metal having an electrolytically-polished inner surface. In addition, JP 4459752 B2 also discloses that the bottling step and the sealing step are performed after the sterilization treatment in the same way as the above.
According to the production methods disclosed in JP 3477468 B2 and JP 4459752 B2, it is possible to obtain a standard seawater solution of good quality as an indicator for measuring the concentration of a nutrient salt in actual seawater as a sample, and it can be expected that the production methods are useful for an appropriate oceanographic survey and the like.